Verapamil and nifedipine are drugs which have the potential to depress myocardial function while also improving coronary artery blood flow and lowering blood pressure which decreases the work of the heart. We studied these two drugs in a model of congestive heart failure to see if either improved or worsened the function of the heart muscle and found that verapamil used in the usual clinical dose caused deterioration in myocardial function while nifedipine improved function. These results suggest verapamil is more dangerous to use than nifedipine in the presence of congestive heart failure.